Compensation for air gap changes and temperature changes in a resonant phase detector

ABSTRACT

A system may include a sensor configured to output a sensor signal indicative of a distance between the sensor and a mechanical member associated with the sensor, a measurement circuit communicatively coupled to the sensor and configured to determine a physical force interaction with the mechanical member based on the sensor signal, and a compensator configured to monitor the sensor signal and to apply a compensation factor to the sensor signal to compensate for changes to properties of the sensor based on at least one of changes in a distance between the sensor and the mechanical member and changes in a temperature associated with the sensor.

RELATED APPLICATION

The present disclosure claims priority to U.S. Provisional PatentApplication Ser. No. 62/856,393, filed Jun. 3, 2019, which isincorporated by reference herein in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates in general to electronic devices withuser interfaces, (e.g., mobile devices, game controllers, instrumentpanels for vehicles, machinery, and/or appliances, etc.), and moreparticularly, resonant phase sensing of resistive-inductive-capacitivesensors for use in a system for mechanical button replacement in amobile device, and/or other suitable applications.

BACKGROUND

Many traditional mobile devices (e.g., mobile phones, personal digitalassistants, video game controllers, etc.) include mechanical buttons toallow for interaction between a user of a mobile device and the mobiledevice itself. However, such mechanical buttons are susceptible toaging, wear, and tear that may reduce the useful life of a mobile deviceand/or may require significant repair if malfunction occurs. Also, thepresence of mechanical buttons may render it difficult to manufacturemobile devices that are waterproof. Accordingly, mobile devicemanufacturers are increasingly looking to equip mobile devices withvirtual buttons that act as a human-machine interface allowing forinteraction between a user of a mobile device and the mobile deviceitself. Similarly, mobile device manufacturers are increasingly lookingto equip mobile devices with other virtual interface areas (e.g., avirtual slider, interface areas of a body of the mobile device otherthan a touch screen, etc.). Ideally, for best user experience, suchvirtual interface areas should look and feel to a user as if amechanical button or other mechanical interface were present instead ofa virtual button or virtual interface area.

Presently, linear resonant actuators (LRAs) and other vibrationalactuators (e.g., rotational actuators, vibrating motors, etc.) areincreasingly being used in mobile devices to generate vibrationalfeedback in response to user interaction with human-machine interfacesof such devices. Typically, a sensor (traditionally a force or pressuresensor) detects user interaction with the device (e.g., a finger presson a virtual button of the device) and in response thereto, the linearresonant actuator may vibrate to provide feedback to the user. Forexample, a linear resonant actuator may vibrate in response to userinteraction with the human-machine interface to mimic to the user thefeel of a mechanical button click.

However, there is a need in the industry for sensors to detect userinteraction with a human-machine interface, wherein such sensors provideacceptable levels of sensor sensitivity, power consumption, and size.

SUMMARY

In accordance with the teachings of the present disclosure, thedisadvantages and problems associated with sensing of human-machineinterface interactions in a mobile device may be reduced or eliminated.

In accordance with embodiments of the present disclosure, a system mayinclude a sensor configured to output a sensor signal indicative of adistance between the sensor and a mechanical member associated with thesensor, a measurement circuit communicatively coupled to the sensor andconfigured to determine a physical force interaction with the mechanicalmember based on the sensor signal, and a compensator configured tomonitor the sensor signal and to apply a compensation factor to thesensor signal to compensate for changes to properties of the sensorbased on at least one of changes in a distance between the sensor andthe mechanical member and changes in a temperature associated with thesensor.

In accordance with embodiments of the present disclosure, a method mayinclude, in a system comprising a sensor configured to output a sensorsignal indicative of a distance between the sensor and a mechanicalmember associated with the sensor and a measurement circuitcommunicatively coupled to the sensor and configured to determine aphysical force interaction with the mechanical member based on thesensor signal, monitoring the sensor signal and applying a compensationfactor to the sensor signal to compensate for changes to properties ofthe sensor based on at least one of changes in a distance between thesensor and the mechanical member and changes in a temperature associatedwith the sensor.

Technical advantages of the present disclosure may be readily apparentto one having ordinary skill in the art from the figures, descriptionand claims included herein. The objects and advantages of theembodiments will be realized and achieved at least by the elements,features, and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates a block diagram of selected components of an examplemobile device, in accordance with embodiments of the present disclosure;

FIG. 2 illustrates a mechanical member separated by a distance from aninductive coil, in accordance with embodiments of the presentdisclosure;

FIG. 3 illustrates selected components of a model for a mechanicalmember and inductive coil that may be used in an inductive sensingsystem, in accordance with embodiments of the present disclosure;

FIG. 4 illustrates selected components of an exampleresistive-inductive-capacitive sensor, in accordance with embodiments ofthe present disclosure; Each of FIGS. 5A-5C illustrates a diagram ofselected components of an example resonant phase sensing system, inaccordance with embodiments of the present disclosure;

FIG. 6 illustrates a diagram of selected components of an exampleresonant phase sensing system implementing time-division multiplexedprocessing of multiple resistive-inductive-capacitive sensors, inaccordance with embodiments of the present disclosure; and

FIG. 7 illustrates a block diagram of selected components of an examplecompensator, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a block diagram of selected components of an examplemobile device 102, in accordance with embodiments of the presentdisclosure. As shown in FIG. 1, mobile device 102 may comprise anenclosure 101, a controller 103, a memory 104, a mechanical member 105,a microphone 106, a linear resonant actuator 107, a radiotransmitter/receiver 108, a speaker 110, and a resonant phase sensingsystem 112.

Enclosure 101 may comprise any suitable housing, casing, or otherenclosure for housing the various components of mobile device 102.Enclosure 101 may be constructed from plastic, metal, and/or any othersuitable materials. In addition, enclosure 101 may be adapted (e.g.,sized and shaped) such that mobile device 102 is readily transported ona person of a user of mobile device 102. Accordingly, mobile device 102may include but is not limited to a smart phone, a tablet computingdevice, a handheld computing device, a personal digital assistant, anotebook computer, a video game controller, or any other device that maybe readily transported on a person of a user of mobile device 102.

Controller 103 may be housed within enclosure 101 and may include anysystem, device, or apparatus configured to interpret and/or executeprogram instructions and/or process data, and may include, withoutlimitation a microprocessor, microcontroller, digital signal processor(DSP), application specific integrated circuit (ASIC), or any otherdigital or analog circuitry configured to interpret and/or executeprogram instructions and/or process data. In some embodiments,controller 103 may interpret and/or execute program instructions and/orprocess data stored in memory 104 and/or other computer-readable mediaaccessible to controller 103.

Memory 104 may be housed within enclosure 101, may be communicativelycoupled to controller 103, and may include any system, device, orapparatus configured to retain program instructions and/or data for aperiod of time (e.g., computer-readable media). Memory 104 may includerandom access memory (RAM), electrically erasable programmable read-onlymemory (EEPROM), a Personal Computer Memory Card InternationalAssociation (PCMCIA) card, flash memory, magnetic storage, opto-magneticstorage, or any suitable selection and/or array of volatile ornon-volatile memory that retains data after power to mobile device 102is turned off.

Microphone 106 may be housed at least partially within enclosure 101,may be communicatively coupled to controller 103, and may comprise anysystem, device, or apparatus configured to convert sound incident atmicrophone 106 to an electrical signal that may be processed bycontroller 103, wherein such sound is converted to an electrical signalusing a diaphragm or membrane having an electrical capacitance thatvaries based on sonic vibrations received at the diaphragm or membrane.Microphone 106 may include an electrostatic microphone, a condensermicrophone, an electret microphone, a microelectromechanical systems(MEMs) microphone, or any other suitable capacitive microphone.

Radio transmitter/receiver 108 may be housed within enclosure 101, maybe communicatively coupled to controller 103, and may include anysystem, device, or apparatus configured to, with the aid of an antenna,generate and transmit radio-frequency signals as well as receiveradio-frequency signals and convert the information carried by suchreceived signals into a form usable by controller 103. Radiotransmitter/receiver 108 may be configured to transmit and/or receivevarious types of radio-frequency signals, including without limitation,cellular communications (e.g., 2G, 3G, 4G, LTE, etc.), short-rangewireless communications (e.g., BLUETOOTH), commercial radio signals,television signals, satellite radio signals (e.g., GPS), WirelessFidelity, etc.

A speaker 110 may be housed at least partially within enclosure 101 ormay be external to enclosure 101, may be communicatively coupled tocontroller 103, and may comprise any system, device, or apparatusconfigured to produce sound in response to electrical audio signalinput. In some embodiments, a speaker may comprise a dynamicloudspeaker, which employs a lightweight diaphragm mechanically coupledto a rigid frame via a flexible suspension that constrains a voice coilto move axially through a cylindrical magnetic gap. When an electricalsignal is applied to the voice coil, a magnetic field is created by theelectric current in the voice coil, making it a variable electromagnet.The voice coil and the driver's magnetic system interact, generating amechanical force that causes the voice coil (and thus, the attachedcone) to move back and forth, thereby reproducing sound under thecontrol of the applied electrical signal coming from the amplifier.

Mechanical member 105 may be housed within or upon enclosure 101, andmay include any suitable system, device, or apparatus configured suchthat all or a portion of mechanical member 105 displaces in positionresponsive to a force, a pressure, or a touch applied upon orproximately to mechanical member 105. In some embodiments, mechanicalmember 105 may be designed to appear as a mechanical button on theexterior of enclosure 101.

Linear resonant actuator 107 may be housed within enclosure 101, and mayinclude any suitable system, device, or apparatus for producing anoscillating mechanical force across a single axis. For example, in someembodiments, linear resonant actuator 107 may rely on an alternatingcurrent voltage to drive a voice coil pressed against a moving massconnected to a spring. When the voice coil is driven at the resonantfrequency of the spring, linear resonant actuator 107 may vibrate with aperceptible force. Thus, linear resonant actuator 107 may be useful inhaptic applications within a specific frequency range. While, for thepurposes of clarity and exposition, this disclosure is described inrelation to the use of linear resonant actuator 107, it is understoodthat any other type or types of vibrational actuators (e.g., eccentricrotating mass actuators) may be used in lieu of or in addition to linearresonant actuator 107. In addition, it is also understood that actuatorsarranged to produce an oscillating mechanical force across multiple axesmay be used in lieu of or in addition to linear resonant actuator 107.As described elsewhere in this disclosure, a linear resonant actuator107, based on a signal received from resonant phase sensing system 112,may render haptic feedback to a user of mobile device 102 for at leastone of mechanical button replacement and capacitive sensor feedback.

Together, mechanical member 105 and linear resonant actuator 107 mayform a human-interface device, such as a virtual interface (e.g., avirtual button), which, to a user of mobile device 102, has a look andfeel of a mechanical button or other mechanical interface of mobiledevice 102.

Resonant phase sensing system 112 may be housed within enclosure 101,may be communicatively coupled to mechanical member 105 and linearresonant actuator 107, and may include any system, device, or apparatusconfigured to detect a displacement of mechanical member 105 indicativeof a physical interaction (e.g., by a user of mobile device 102) withthe human-machine interface of mobile device 102 (e.g., a force appliedby a human finger to a virtual interface of mobile device 102). Asdescribed in greater detail below, resonant phase sensing system 112 maydetect displacement of mechanical member 105 by performing resonantphase sensing of a resistive-inductive-capacitive sensor for which animpedance (e.g., inductance, capacitance, and/or resistance) of theresistive-inductive-capacitive sensor changes in response todisplacement of mechanical member 105. Thus, mechanical member 105 maycomprise any suitable system, device, or apparatus which all or aportion thereof may displace, and such displacement may cause a changein an impedance of a resistive-inductive-capacitive sensor integral toresonant phase sensing system 112. Resonant phase sensing system 112 mayalso generate an electronic signal for driving linear resonant actuator107 in response to a physical interaction associated with ahuman-machine interface associated with mechanical member 105. Detail ofan example resonant phase sensing system 112 in accordance withembodiments of the present disclosure is depicted in greater detailbelow.

Although specific example components are depicted in FIG. 1 as beingintegral to mobile device 102 (e.g., controller 103, memory 104,mechanical member 105, microphone 106, radio transmitter/receiver 108,speakers(s) 110, linear resonant actuator 107, etc.), a mobile device102 in accordance with this disclosure may comprise one or morecomponents not specifically enumerated above. For example, although FIG.1 depicts certain user interface components, mobile device 102 mayinclude one or more other user interface components in addition to thosedepicted in FIG. 1, including but not limited to a keypad, a touchscreen, and a display, thus allowing a user to interact with and/orotherwise manipulate mobile device 102 and its associated components. Inaddition, although FIG. 1 depicts only a single virtual buttoncomprising mechanical member 105 and linear resonant actuator 107 forpurposes of clarity and exposition, in some embodiments a mobile device102 may have multiple virtual interfaces each comprising a respectivemechanical member 105 and linear resonant actuator 107.

Although, as stated above, resonant phase sensing system 112 may detectdisplacement of mechanical member 105 by performing resonant phasesensing of a resistive-inductive-capacitive sensor for which animpedance (e.g., inductance, capacitance, and/or resistance) of theresistive-inductive-capacitive sensor changes in response todisplacement of mechanical member 105, in some embodiments resonantphase sensing system 112 may primarily detect displacement of mechanicalmember 105 by using resonant phase sensing to determine a change in aninductance of a resistive-inductive-capacitive sensor. For example,FIGS. 2 and 3 illustrate selected components of an example inductivesensing application that may be implemented by resonant phase sensingsystem 112, in accordance with embodiments of the present disclosure.

Although the foregoing contemplates a resonant phase sensing system 112for use in a mobile device 102, the resonant phase sensing system 112may be used in any other suitable host device. A host device may includewithout limitation, a portable and/or battery-powered mobile computingdevice (e.g., a laptop, notebook, or tablet computer), a gaming console,a remote control device, a home automation controller, a domesticappliance (e.g., domestic temperature or lighting control system), atoy, a machine (e.g., a robot), an audio player, a video player, and amobile telephone (e.g., a smartphone).

FIG. 2 illustrates mechanical member 105 embodied as a metal plateseparated by a distance d from an inductive coil 202, in accordance withembodiments of the present disclosure. FIG. 3 illustrates selectedcomponents of a model for mechanical member 105 and inductive coil 202that may be used in an inductive sensing system 300, in accordance withembodiments of the present disclosure. As shown in FIG. 3, inductivesensing system 300 may include mechanical member 105, modeled as avariable electrical resistance 304 and a variable electrical inductance306, and may include inductive coil 202 in physical proximity tomechanical member 105 such that inductive coil 202 has a mutualinductance with mechanical member 105 defined by a variable couplingcoefficient k. As shown in FIG. 3, inductive coil 202 may be modeled asa variable electrical inductance 308 and a variable electricalresistance 310.

In operation, as a current I flows through inductive coil 202, suchcurrent may induce a magnetic field which in turn may induce an eddycurrent inside mechanical member 105. When a force is applied to and/orremoved from mechanical member 105, which alters distance d betweenmechanical member 105 and inductive coil 202, the coupling coefficientk, variable electrical resistance 304, and/or variable electricalinductance 306 may also change in response to the change in distance.These changes in the various electrical parameters may, in turn, modifyan effective impedance Z_(L) of inductive coil 202.

FIG. 4 illustrates selected components of an exampleresistive-inductive-capacitive sensor 402, in accordance withembodiments of the present disclosure. As shown in FIG. 4,resistive-inductive-capacitive sensor 402 may include mechanical member105, inductive coil 202, a resistor 404, and capacitor 406, whereinmechanical member 105 and inductive coil 202 have a variable couplingcoefficient k. Although shown in FIG. 4 to be arranged in parallel withone another, it is understood that inductive coil 202, resistor 404, andcapacitor 406 may be arranged in any other suitable manner that allowsresistive-inductive-capacitive sensor 402 to act as a resonant tank. Forexample, in some embodiments, inductive coil 202, resistor 404, andcapacitor 406 may be arranged in series with one another. In someembodiments, resistor 404 may not be implemented with a stand-aloneresistor, but may instead be implemented by a parasitic resistance ofinductive coil 202, a parasitic resistance of capacitor 406, and/or anyother suitable parasitic resistance.

FIG. 5A illustrates a diagram of selected components of an exampleresonant phase sensing system 112A, in accordance with embodiments ofthe present disclosure. In some embodiments, resonant phase sensingsystem 112A may be used to implement resonant phase sensing system 112of FIG. 1. As shown FIG. 5A, resonant phase sensing system 112A mayinclude a resistive-inductive-capacitive sensor 402 and a processingintegrated circuit (IC) 512A.

Processing IC 512A may be communicatively coupled toresistive-inductive-capacitive sensor 402 and may comprise any suitablesystem, device, or apparatus configured to implement a measurementcircuit to measure phase information associated withresistive-inductive-capacitive sensor 402 and based on the phaseinformation, determine a displacement of mechanical member 105 relativeto resistive-inductive-capacitive sensor 402. Thus, processing IC 512Amay be configured to determine an occurrence of a physical interaction(e.g., press or release of a virtual button) associated with ahuman-machine interface associated with mechanical member 105 based onthe phase information.

As shown in FIG. 5A, processing IC 512A may include a phase shifter 510,a voltage-to-current (V-I) converter 508, a preamplifier 540, anintermediate frequency mixer 542, a combiner 544, a programmable gainamplifier (PGA) 514, an oscillator 516, a phase shifter 518, anamplitude and phase calculation block 531, a DSP 532, a low-pass filter534, a combiner 550, and a compensator 552. Processing IC 512A may alsoinclude a coherent incident/quadrature detector implemented with anincident channel comprising a mixer 520, a low-pass filter 524, and ananalog-to-digital converter (ADC) 528, and a quadrature channelcomprising a mixer 522, a low-pass filter 526, and an ADC 530 such thatprocessing IC 512A is configured to measure the phase information usingthe coherent incident/quadrature detector.

Phase shifter 510 may include any system, device, or apparatusconfigured to receive an oscillation signal generated by processing IC512A (as explained in greater detail below) and phase shift suchoscillation signal such that at an operating frequency of resonant phasesensing system 112, an incident component of a sensor signal ϕ generatedby pre-amplifier 540 is approximately equal to a quadrature component ofsensor signal ϕ, so as to provide common mode noise rejection by a phasedetector implemented by processing IC 512A, as described in greaterdetail below.

V-I converter 508 may receive the phase shifted oscillation signal fromphase shifter 510, which may be a voltage signal, convert the voltagesignal to a corresponding current signal, and drive the current signalon resistive-inductive-capacitive sensor 402 at a driving frequency withthe phase-shifted oscillation signal in order to generate sensor signalϕ which may be processed by processing IC 512A, as described in greaterdetail below. In some embodiments, a driving frequency of thephase-shifted oscillation signal may be selected based on a resonantfrequency of resistive-inductive-capacitive sensor 402 (e.g., may beapproximately equal to the resonant frequency ofresistive-inductive-capacitive sensor 402).

Preamplifier 540 may receive sensor signal ϕ and condition sensor signalϕ for frequency mixing, with mixer 542, to an intermediate frequency Δfcombined by combiner 544 with an oscillation frequency generated byoscillator 516, as described in greater detail below, whereinintermediate frequency Δf is significantly less than the oscillationfrequency. In some embodiments, preamplifier 540, mixer 542, andcombiner 544 may not be present, in which case PGA 514 may receivesensor signal ϕ directly from resistive-inductive-capacitive sensor 402.However, when present, preamplifier 540, mixer 542, and combiner 544 mayallow for mixing sensor signal ϕ down to a lower intermediate frequencyΔf which may allow for lower-bandwidth and more efficient ADCs (e.g.,ADCs 528 and 530 of FIGS. 5A and 5B and ADC 529 of FIG. 5C, describedbelow) and/or which may allow for minimization of phase and/or gainmismatches in the incident and quadrature paths of the phase detector ofprocessing IC 512A.

In operation, PGA 514 may further amplify sensor signal ϕ to conditionsensor signal ϕ for processing by the coherent incident/quadraturedetector. Oscillator 516 may generate an oscillation signal to be usedas a basis for the signal driven by V-I converter 508, as well as theoscillation signals used by mixers 520 and 522 to extract incident andquadrature components of amplified sensor signal ϕ. As shown in FIG. 5A,mixer 520 of the incident channel may use an unshifted version of theoscillation signal generated by oscillator 516, while mixer 522 of thequadrature channel may use a 90-degree shifted version of theoscillation signal phase shifted by phase shifter 518. As mentionedabove, the oscillation frequency of the oscillation signal generated byoscillator 516 may be selected based on a resonant frequency ofresistive-inductive-capacitive sensor 402 (e.g., may be approximatelyequal to the resonant frequency of resistive-inductive-capacitive sensor402). In some embodiments, oscillator 516 may be implemented with avoltage-controlled oscillator (VCO). In other embodiments, oscillator516 may be implemented with a digitally-controlled oscillator (DCO).

In the incident channel, mixer 520 may extract the incident component ofamplified sensor signal 4, low-pass filter 524 may filter out theoscillation signal mixed with the amplified sensor signal ϕ to generatea direct current (DC) incident component, and ADC 528 may convert suchDC incident component into an equivalent incident component digitalsignal for processing by amplitude and phase calculation block 531.Similarly, in the quadrature channel, mixer 522 may extract thequadrature component of amplified sensor signal ϕ, low-pass filter 526may filter out the phase-shifted oscillation signal mixed with theamplified sensor signal ϕ to generate a direct current (DC) quadraturecomponent, and ADC 530 may convert such DC quadrature component into anequivalent quadrature component digital signal for processing byamplitude and phase calculation block 531.

Amplitude and phase calculation block 531 may include any system,device, or apparatus configured to receive phase information comprisingthe incident component digital signal and the quadrature componentdigital signal and based thereon, extract amplitude and phaseinformation.

DSP 532 may include any system, device, or apparatus configured tointerpret and/or execute program instructions and/or process data. Inparticular, DSP 532 may receive the phase information and the amplitudeinformation generated by amplitude and phase calculation block 531 andbased thereon, determine a displacement of mechanical member 105relative to resistive-inductive-capacitive sensor 402, which may beindicative of an occurrence of a physical interaction (e.g., press orrelease of a virtual button or other interaction with a virtualinterface) associated with a human-machine interface associated withmechanical member 105 based on the phase information. DSP 532 may alsogenerate an output signal indicative of the displacement. In someembodiments, such output signal may comprise a control signal forcontrolling mechanical vibration of linear resonant actuator 107 inresponse to the displacement.

Compensator 552 may comprise any system, device, or apparatus which maytrack changes in properties of resistive-inductive-capacitive sensor 402due to either or both of a change in a gap (e.g., an air gap) betweenmechanical member 105 and inductive coil 202 and a change in atemperature associated with resistive-inductive-capacitive sensor 402,and which may further apply dynamic compensation such that under changesin such properties, the resonant phase sensing system 112 provides aconsistent response indicative of human interaction with a virtualbutton.

Combiner 550 may subtract the phase information generated by amplitudeand phase calculation block 531 from a reference phase ϕ_(ref) in orderto generate an error signal that may be received by low-pass filter 534.Low-pass filter 534 may low-pass filter the error signal, and suchfiltered error signal may be applied to oscillator 516 to modify thefrequency of the oscillation signal generated by oscillator 516, inorder to drive sensor signal ϕ towards reference phase ϕ_(ref). As aresult, sensor signal ϕ may comprise a transient decaying signal inresponse to a “press” of a virtual button (or other interaction with avirtual interface) associated with resonant phase sensing system 112A aswell as another transient decaying signal in response to a subsequent“release” of the virtual button (or other interaction with a virtualinterface). Accordingly, low-pass filter 534 in connection withoscillator 516 may implement a feedback control loop that may trackchanges in operating parameters of resonant phase sensing system 112A bymodifying the driving frequency of oscillator 516.

FIG. 5B illustrates a diagram of selected components of an exampleresonant phase sensing system 112B, in accordance with embodiments ofthe present disclosure. In some embodiments, resonant phase sensingsystem 112B may be used to implement resonant phase sensing system 112of FIG. 1. Resonant phase sensing system 112B of FIG. 5B may be, in manyrespects, similar to resonant phase sensing system 112A of FIG. 5A.Accordingly, only those differences between resonant phase sensingsystem 112B and resonant phase sensing system 112A may be describedbelow. As shown FIG. 5B, resonant phase sensing system 112B may includeprocessing IC 512B in lieu of processing IC 512A. Processing IC 512B ofFIG. 5B may be, in many respects, similar to processing IC 512A of FIG.5A. Accordingly, only those differences between processing IC 512B andprocessing IC 512A may be described below.

Processing IC 512B may include variable phase shifter 519. Thus, inoperation, oscillator 516 may drive a driving signal and oscillationsignal which variable phase shifter 519 may phase shift to generateoscillation signals to be mixed by mixers 520 and 522. Similar to thatof processing IC 512A, low-pass filter 534 may low-pass filter an errorsignal based on phase information extracted by amplitude and phasecalculation block 531, but instead such filtered error signal may beapplied to variable phase shifter 519 to modify the phase offset of theoscillation signal generated by oscillator 516, in order to drive sensorsignal ϕ towards indicating a phase shift of zero. As a result, sensorsignal ϕ may comprise a transient decaying signal in response to a“press” of a virtual button (or other interaction with a virtualinterface) associated with resonant phase sensing system 112B as well asanother transient decaying signal in response to a subsequent “release”of the virtual button (or other interaction with a virtual interface).Accordingly, low-pass filter 534 in connection with variable phaseshifter 519 may implement a feedback control loop that may track changesin operating parameters of resonant phase sensing system 112B bymodifying the phase shift applied by variable phase shifter 519.

FIG. 5C illustrates a diagram of selected components of an exampleresonant phase sensing system 112C, in accordance with embodiments ofthe present disclosure. In some embodiments, resonant phase sensingsystem 112C may be used to implement resonant phase sensing system 112of FIG. 1. Resonant phase sensing system 112C of FIG. 5C may be, in manyrespects, similar to resonant phase sensing system 112A of FIG. 5A.Accordingly, only those differences between resonant phase sensingsystem 112C and resonant phase sensing system 112A may be describedbelow. For example, a particular difference between resonant phasesensing system 112C and resonant phase sensing system 112A is thatresonant phase sensing system 112C may include ADC 529 and ADC 541 inlieu of ADC 528 and ADC 530. Accordingly, a coherent incident/quadraturedetector for resonant phase sensing system 112C may be implemented withan incident channel comprising a digital mixer 521 and a digitallow-pass filter 525 (in lieu of analog mixer 520 and analog low-passfilter 524) and a quadrature channel comprising a digital mixer 523 anda low-pass filter 527 (in lieu of analog mixer 522 and analog low-passfilter 526) such that processing IC 512C is configured to measure thephase information using such coherent incident/quadrature detector.Although not explicitly shown, resonant phase sensing system 112B couldbe modified in a manner similar to that of how resonant phase sensingsystem 112A is shown to be modified to result in resonant phase sensingsystem 112C.

FIG. 6 illustrates a diagram of selected components of an exampleresonant phase sensing system 112D implementing time-divisionmultiplexed processing of multiple resistive-inductive-capacitivesensors 402 (e.g., resistive-inductive-capacitive sensors 402A-402Nshown in FIG. 6), in accordance with embodiments of the presentdisclosure. In some embodiments, resonant phase sensing system 112D maybe used to implement resonant phase sensing system 112 of FIG. 1.Resonant phase sensing system 112D of FIG. 6 may be, in many respects,similar to resonant phase sensing system 112A of FIG. 5A. Accordingly,only those differences between resonant phase sensing system 112D andresonant phase sensing system 112A may be described below. Inparticular, resonant phase sensing system 112D may include a pluralityof resistive-inductive-capacitive sensors 402 (e.g.,resistive-inductive-capacitive sensors 402A-402N shown in FIG. 6) inlieu of the single resistive-inductive-capacitive sensor 402 shown inFIG. 5A. In addition, resonant phase sensing system 112D may includemultiplexers 602 and 604, each of which may select an output signal froma plurality of input signals responsive to a control signal SELECT(which may be controlled by a time-division multiplexing controlsubsystem implemented by controller 103 or another suitable component ofmobile device 102). Thus, while in some embodiments a device such asmobile device 102 may comprise a plurality ofresistive-inductive-capacitive sensors 402 which may be simultaneouslydriven and separately processed by a respective processing IC, in otherembodiments a resonant phase sensing system (e.g., resonant phasesensing system 112D) may drive resistive-inductive-capacitive sensors402 in a time-division multiplexed manner Such approach may reduce powerconsumption and device size as compared with multiple-sensorimplementations in which the multiple sensors are simultaneously drivenand/or sensed. Device size may be reduced by time-division multiplexingmultiple sensors into a single driver and measurement circuit channel,wherein only a single driver and a single measurement circuit may berequired, thus minimizing an amount of integrated circuit area needed toperform driving and measurement. In addition, by leveraging a singledriver and measurement circuit, no calibration may be needed to adjustfor mismatches and/or errors between different drivers and/or differentmeasurement circuits.

For purposes of clarity and exposition, preamplifier 440, mixer 442, andcombiner 444 have been excluded from FIG. 6. However, in someembodiments, processing IC 512D may include preamplifier 440, mixer 442,and combiner 444 similar to that depicted in FIGS. 5A-5C.

In resonant phase sensing system 112D, when a firstresistive-inductive-capacitive sensor (e.g.,resistive-inductive-capacitive sensor 402A) is selected by thetime-division multiplexing control subsystem for being driven by V-Iconverter 508 and measured by the measurement circuit implemented byprocessing IC 512D, other resistive-inductive-capacitive sensors (e.g.,resistive-inductive-capacitive sensors 402N-402N) may each be placed ina low-impedance state. Similarly, when a secondresistive-inductive-capacitive sensor (e.g.,resistive-inductive-capacitive sensor 402B) is selected by thetime-division multiplexing control subsystem for being driven by V-Iconverter 508 and measured by the measurement circuit implemented byprocessing IC 512D, other resistive-inductive-capacitive sensors (e.g.,resistive-inductive-capacitive sensors other than 402B, including 402A)may each be placed in a low-impedance state. Such an approach mayminimize power consumption within unselectedresistive-inductive-capacitive sensors 402.

A similar approach may also be used in a resonant phase sensing systemhaving only a single resistive-inductive-capacitive sensor 402 in orderto reduce power consumption associated with such sensor. For example,instead of time-division multiplexing among multiple sensors, a singleresistive-inductive-capacitive sensor 402 may be duty-cycled inoperation such that, for a first portion of a cycle of a measurementcircuit (e.g., processing IC 512A), the measurement circuit may operatein a low power mode, and, for a second portion of the cycle of themeasurement circuit, the measurement circuit may operate in a high powermode in which the measurement circuit consumes more power than in thelow power mode, and wherein the measurement circuit performs measurementof the phase information and determination of the displacement of amechanical member (e.g., mechanical member 105) during the secondportion.

Although not explicitly shown, resonant phase sensing system 112B couldbe modified in a manner similar to that of how resonant phase sensingsystem 112A is shown to be modified to result in resonant phase sensingsystem 112D, such that resonant phase sensing system 112B couldimplement time-division multiplexed sensing on a plurality ofresistive-inductive-capacitive sensors 402. Similarly, although notexplicitly shown, resonant phase sensing system 112C could be modifiedin a manner similar to that of how resonant phase sensing system 112A isshown to be modified to result in resonant phase sensing system 112D,such that resonant phase sensing system 112C could implementtime-division multiplexed sensing on a plurality ofresistive-inductive-capacitive sensors 402.

A resistive-inductive-capacitive sensor 402 used as a virtual buttontypically relies on an air gap or compressible spacer between mechanicalmember 105 and inductive coil 202, such that mechanical member 105 maybe deflected inward towards inductive coil 202 with an applied force.However, both static and dynamic changes in the distance of the gapbetween mechanical member 105 and inductive coil 202 may change thesensitivity of the sensor. For example, due to changes in temperatureproximate to resistive-inductive-capacitive sensor 402, thermalexpansion of materials making up resistive-inductive-capacitive sensor402 may cause a change in such gap (e.g., a change in distance d). Asanother example, deformation of mechanical member 105 or damage (e.g., adent) to mechanical member 105 may also cause a change in such gap(e.g., a change in distance d). In addition, as is desired to make phasemeasurements indicative of human interaction with mechanical member 105,mechanical interaction of a human or another object with mechanicalmember 105 may also cause a change in such gap (e.g., a change indistance d).

Analysis of resistive-inductive-capacitive sensor 402 may show that aquality factor Q, inductance L, and inductance shift (ΔL/L) for a givendisplacement of mechanical member 105 are a function of the gap betweenmechanical member 105 and inductive coil 202. Thus, with a reduction inthe gap distance between mechanical member 105 and inductive coil 202:

-   -   Sensor inductance L may decrease due to increased mutual        inductance;    -   Inductance shift (ΔL/L) sensitivity may increase for a given        inflection due to improved electrical coupling between        mechanical member 105 and inductive coil 202; and    -   Quality factor Q may decrease due to reduction in sensor        inductance L and an increase in the alternating current (AC)        series resistance of inductive coil 202, where quality factor Q        may be given by Q=ωL/R_(S), where ω is the angular frequency at        which resistive-inductive-capacitive sensor 402 is driven, and        R_(S) is a cumulative AC series resistance and direct        current (DC) resistance of inductive coil 202.

A measured phase change of resistive-inductive-capacitive sensor 402 maybe a function of inductance shift (ΔL/L) for a given inflection andquality factor Q.

Further, quality factor Q may also vary with temperature, due to anelectrical conductivity coefficient of a conductor used to manufactureinductive coil 202. Such variance may manifest as a DC resistance thatmay be variable as a function of temperature. In particular, a highersensor temperature may increase inductive coil 202 DC resistance whichmay reduce quality factor Q, and a lower sensor temperature may decreaseinductive coil 202 DC resistance which may increase quality factor Q.

Due to variance of quality factor Q with temperature, quality factor Qand other sensor parameters may be used to estimate a temperatureassociated with resistive-inductive-capacitive sensor 402. Becauseinitial sensor parameters (e.g., initial sensor properties 716, asdescribed below) may be stored during a calibration phase, qualityfactor Q and other sensor parameters can be captured at a knowntemperature. Even through quality factor Q may change throughout thelifetime of resistive-inductive-capacitive sensor 402 due to both airgap and temperature changes, contribution to changes in quality factor Qfrom each of these components may be separated. For example, becauseresistive-inductive-capacitive sensor 402 may be a second-orderinductive-capacitive system, change in quality factor Q due to a changein air gap can be predicted by a measured change in resonance frequencyf₀. Thus, if quality factor Q changes by more than the predicted amountfor a change in resonance frequency f₀, then the remainder change inquality factor Q may be due to change in temperature ofresistive-inductive-capacitive sensor 402. Accordingly, comparing thechange in quality factor Q due to temperature to initial sensorparameters may provide the portion of the change in quality factor Qattributable to change in temperature. If a temperature conductivitycoefficient of metal which makes up resistive-inductive-capacitivesensor 402 (e.g., inductive coil 202) is known, then a change in qualityfactor Q due to a change of series resistance of inductive coil 202 maybe known. Thus, a temperature of resistive-inductive-capacitive sensor402 may be determined regardless of air gap or any other factors thatmay manifest as a change in resonant frequency f₀.

FIG. 7 illustrates a block diagram of selected components of an examplecompensator 552, in accordance with embodiments of the presentdisclosure. As described above, compensator 552 may be configured tocompensate for changes in sensor inductance L, inductance shift (ΔL/L),and quality factor Q due to changes in the gap between mechanical member105 and inductive coil 202.

As shown in FIG. 7, compensator 552 may include correction factorcalculator 702, quality factor detector 704, resonance change tracker706, impedance calculator 708, inductance calculator 710, gap calculator712, and channel ratio comparator 714. As described in greater detailbelow, correction factor calculator 702 may use a change in inductanceof resistive-inductive-capacitor sensor 402, change in quality factor Qof resistive-inductive-capacitor sensor 402, change in resonantfrequency of resistive-inductive-capacitor sensor 402, and change in anyother suitable properties of resistive-inductive-capacitor sensor 402 incomparison with initial sensor properties 716 ofresistive-inductive-capacitor sensor 402 (which may be stored in amemory integral to or otherwise accessible to compensator 552) tocorrect for measurement sensitivity changes caused by changes in gapdistance between mechanical member 105 and inductive coil 202 and/ortemperature.

Quality factor detector 704 may comprise any suitable system, device, orapparatus configured to determine a quality factor forresistive-inductive-capacitor sensor 402. For example, in someembodiments, quality factor detector 704 may extract the quality factorby tracking a phase slope for resistive-inductive-capacitor sensor 402during a change in driving frequency of resistive-inductive-capacitorsensor 402. In these and other embodiments, quality factor detector 704may be implemented in accordance with the methods and systems disclosedin U.S. patent application Ser. No. 16/354,695 filed Mar. 15, 2019, andincorporated by reference herein in its entirety.

Resonance change tracker 706 may monitor changes to the drivingfrequency set by variable oscillator 516. As described herein, thefeedback loop formed in part by combiner 450 and low-pass filter 434 mayserve to track a resonant frequency of resistive-inductive-capacitorsensor 402 and control the driving frequency ofresistive-inductive-capacitor sensor 402 which is established byoscillator 516. Accordingly, resonance change tracker 706 may monitorsuch resonant frequency, track changes to such resonant frequency overtime, and communicate signals to correction factor calculator 702indicative of such changes.

As described above, a memory may store initial sensor properties 716.Initial sensor properties 716 may include various properties associatedwith resistive-inductive-capacitor sensor 402 with mechanical member 105in a resting state in which it is not being acted upon by a human orother mechanical stimulus. Such properties may comprise an initialquality factor Q_(init), inductance L_(init), resonant frequencyf_(init), tank capacitance C_(init), and/or one or more other propertiesof resistive-inductive-capacitor sensor 402. Such properties may bedetermined during a calibration sequence of resonant phase sensingsystem 112 or otherwise provided to compensator 552 as defaultproperties.

In operation, one or both of quality factor detector 704 and resonancechange tracker 706 may be used to trigger calculation of a correctionfactor by correction factor calculator 702 in response to the existenceof one or more triggering conditions. The one or more triggeringconditions may include, without limitation:

-   -   a change in resonant frequency of resistive-inductive-capacitor        sensor 402 by more than a threshold amount;    -   a change in quality factor Q of resistive-inductive-capacitor        sensor 402 by more than a threshold amount;    -   a change in resonant frequency of resistive-inductive-capacitor        sensor 402 at a rate outside of a predetermined range; and    -   a change in quality factor Q of resistive-inductive-capacitor        sensor 402 at a rate outside of a predetermined range.

In one example scenario, if resonance change tracker 706 detects achange in resonant frequency of resistive-inductive-capacitor sensor 402due to a deflection caused by intentional human interaction, the systemtime constants of resonant phase sensing system 112 may be fast enoughand/or change in resonant frequency may be small enough such that notriggering of calculation of a correction factor may occur. Because onlythe contribution of resistive-inductive-capacitor sensor 402 to thechange in resonant frequency may be desired, the change in resonantfrequency may be determined by removing any on-chip effects withinresonant phase sensing system 112 that may have added to the change inresonant frequency, including without limitation temperature-inducedchanges in resonant frequency.

For example, in some embodiments, compensator 552 may measure resonantfrequency f_(new) of resistive-inductive-capacitor sensor 402 andcalculate a change M in the frequency by subtracting apreviously-measured frequency f_(old) from the measured resonantfrequency f_(new). Compensator 552 may further subtract undesired systemfrequency change effects Δf_(chip), such as temperature-induced changes,from the measured change Δf, the net result being a change in frequencyΔf_(sensor) attributable solely to the change in resonance ofresistive-inductive-capacitor sensor 402. With change in frequencyΔf_(sensor) known, it may be assumed that this change in resonancefrequency was caused by a change in inductance ΔL ofresistive-inductive-capacitor sensor 402, based on the relationshipf=½π√(LC), where C is a tank capacitance ofresistive-inductive-capacitor sensor 402. While a change in tankcapacitance could also manifest as a change in frequency Δf_(sensor),capacitive changes may be relatively small asresistive-inductive-capacitor sensor 402 may be designed to measureinductance with a fixed tank capacitance C. If change in inductance ΔLis positive in value, it may indicate mechanical member 105 moving awayfrom inductive coil 202. If change in inductance ΔL is negative invalue, it may indicate mechanical member 105 moving towards inductivecoil 202. By calculating change in inductance ΔL using a change infrequency Δf_(sensor) measurement, the calculated change in inductanceΔL may be robust against absolute resonant frequency accuracy, as anyunknown resonant frequency offset caused by a digital code or othercontrol signal controlling oscillator 516 may be effectively cancelledby using the change in frequency, rather than an absolute frequencyindicated by such digital code or other control signal.

Alternatively, another approach for extracting inductance L may be used.If tank capacitance C is programmed in initial sensor properties 716,and an absolute accuracy for a digital code or other control signalcontrolling oscillator 516, then a new sensor inductance may be founddirectly based on sensing of an absolute resonant frequency f_(new), andnot the change in frequency Δf_(sensor).

At the time a change in frequency Δf_(sensor) is made, the qualityfactor detector 704 may also measure a quality factor Q ofresistive-inductive-capacitor sensor 402, such that both the resonantfrequency and quality factor Q are known at the same time. By measuringan aggregate quality factor Q, the measured quality factor Q may includeany changes between mechanical member 105 and inductive coil 202 as wellas any temperature effects. With both the change in inductance ΔL andnew measured quality factor Q_(new) known, such parameters may becompared to initial sensor properties 716 to find a new total inductanceL_(new) (L_(new)=ΔL+L_(init)) for resistive-inductive-capacitor sensor402 and a change in quality factor ΔQ (ΔQ=Q_(new)−Q_(init)). Other newextracted parameters may include the change in inductance ΔL against theinitial inductance value L_(init) (ΔL/L_(init)) and against the newinductance value L_(new) (ΔL/L_(new)).

Correction factor calculator 702 may compare initial sensor properties716 and the newly-captured properties to determine appropriatecompensation or correction to be applied to resonant phase sensingsystem 112 including compensation or correction for a signal output byresonant phase sensing system 112 indicative of a human interaction withmechanical member 105. For example, correction factor calculator 702 mayapply one or more of the following compensations and corrections:

-   -   compensation such that changes in a gap between mechanical        member 105 and inductive coil 202 have no effect on virtual        button sensitivity for a given virtual button sensitivity;    -   compensation such that changes in temperature have no effect on        virtual button sensitivity for a given virtual button        sensitivity; and    -   linearization of measured phase information for incremental        changes in the gap between mechanical member 105 and inductive        coil 202 wherein:        -   linear changes in applied sensor force yield linear detected            phase output; and        -   linear changes in sensor deflection yield linear detected            phase output.

Such compensation and/or correction may be applied by one or more ofscaling of the actual measured phase and amplitude information,modification of force detection thresholds for a virtual button, addingoffsets to measured phase and amplitude information, use of digital oranalog filtering, referencing a lookup table for compensation values tobe applied, adjustment of resonant frequency using tuning capacitorswithin and/or changing resistance of resistive-inductive-capacitorsensor 402, and/or any other suitable compensation or correction. Suchcompensation and/or correction may be used to improve user experiencefor a virtual button that responds based on the amount of deflection orforce of applied to the virtual button, improve virtual buttoninteraction detection algorithms by comparing sample to sample phaseinformation, modify virtual button force detection thresholds, analyzephase versus change in deflection slope to adjust performance of keyanalog circuitry blocks of resonant phase sensing system to improvedetection sensitivity, and/or analyze phase versus change in deflectionslope to adjust performance of key analog circuitry blocks of resonantphase sensing system to compare sensitivity between multiple buttons forsensor diagnostics. Benefits of applying compensation and/or correctionbased on sensor gap and temperature may include resonant phasesensing-based virtual buttons that provide an opportunity for more userinteraction than a traditional discrete (e.g., on or off) mechanicalbutton, a consistent user experience across changes in sensorperformance over time, and immunity of user experience from externalfactors.

Impedance calculator 708 may comprise any system, device, or apparatusconfigured to calculate an impedance of resistive-inductive-capacitorsensor 402 based on phase and/or amplitude information processed by DSP532. Inductance calculator 710 may comprise any system, device, orapparatus configured to calculate an inductance ofresistive-inductive-capacitor sensor 402 based on the calculation ofimpedance performed by impedance calculator 708. Gap calculator 712 maycomprise any system, device, or apparatus configured to calculate a gapbetween mechanical member 105 and inductive coil 202 based on thecalculation of inductance performed by inductance calculator 710.Example functionality of impedance calculator 708, inductance calculator710, and gap calculator 712 is further described in greater detailbelow.

Inductive-capacitive tank sensors have a variable impedance versusfrequency which can be simplified to the form Z═R+jX, where Z isimpedance, R is resistance, and X is reactance. At resonance, thereactive component is cancelled, leaving just the resistive term Z=R. Atfrequencies sufficiently below resonance (e.g., 10 times below resonantfrequency), inductance may dominate the reactive portion, and theimpedance can be simplified to Z=R+jωL.

Accordingly, to calculate inductance of resistive-inductive-capacitorsensor 402, resonant phase sensing system 112 may sweep a range offrequencies and impedance calculator 708 may measure impedance Z versusfrequency f (or angular frequency ω=2πf). Impedance calculator 708 mayfurther extract the imagination portion of the impedance, jX, bymeasuring the impedance at two different frequencies and calculating thedifference. With impedance Z measured and drive frequency f known,inductance calculator 710 may calculate inductance L as L=X/ω. Gapcalculator 712 may include or may otherwise have access to apre-characterized lookup table (e.g., inductance versus distance lookuptable), and thus may calculate a gap between mechanical member 105 andinductive coil 202 based on the inductance calculated by inductancecalculator 710.

In other embodiments, with resistive-inductive-capacitor sensor 402being driven by a current source (e.g., V-I converter 508) andprocessing IC 512 measuring a voltage induced onresistive-inductive-capacitor sensor 402, another approach may be usedto measure inductance L and the gap between mechanical member 105 andinductive coil 202. In such approach, impedance calculator 708 may notbe present or needed, and resonant phase sensing system 112 may linearlyincrease a current I_(drive) from a minimum current I_(min) to a maximumcurrent I_(max) over a period of time T_(ramp), during which period oftime T_(ramp) a measured voltage V_(meas) ofresistive-inductive-capacitor sensor 402 should remain constant.Accordingly, inductance calculator 710 may calculate inductance L asL=V_(meas)T_(ramp)/(I_(max)−I_(min)). In turn, gap calculator 712 may(e.g., based on a pre-characterized lookup table) calculate a gapbetween mechanical member 105 and inductive coil 202 based on theinductance calculated by inductance calculator 710.

In these and other embodiments, a variation in air gap may becharacterized and compensated for by performing a calibration (e.g., afactory calibration) with known force levels applied. For example,during a factory calibration, a calibration tool may separately apply atleast two known forces to mechanical member 105, compensator 552 maymeasure the phase response to such applied forces and calculate theslope of phase shift versus force, and may apply a gain correction toeach resistive-inductive-capacitive sensor 402 in order to achieve thedesired phase response as a function of applied force.

In these and other embodiments, in a resonant phase sensing system 112having multiple resistive-inductive-capacitive sensors 402, compensator552 may apply compensation for each resistive-inductive-capacitivesensor 402. For example, during factory calibration, the response ofeach resistive-inductive-capacitive sensor 402 may be calibrated toaccount for gap between mechanical member 105 and inductive coil 202.During factory calibration, compensator 552 may measure the phaseresponse of each resistive-inductive-capacitive sensor 402 responsive toone or more known applied forces, store such phase information in amemory accessible to compensator 552, calculate ratios of phaseresponses between adjacent resistive-inductive-capacitive sensors 402,and store such ratios. During active use, compensator 552 mayperiodically measure the phase response of eachresistive-inductive-capacitive sensor 402 and calculate ratios of phaseresponses between adjacent resistive-inductive-capacitive sensors 402.Due to aging or mechanical damage, a gap between mechanical member 105and inductive coil 202 of one resistive-inductive-capacitive sensor 402may vary over time to a greater extent than anotherresistive-inductive-capacitive sensor 402, resulting in new ratiosbetween adjacent resistive-inductive-capacitive sensors 402. Calculationof new ratios and comparison of such new ratios to those obtained duringfactory calibration may be used to characterize a gap profile for aresistive-inductive-capacitive sensor 402, and compensator 552 may applya gain correction for each resistive-inductive-capacitive sensor 402 toachieve uniform phase responses among resistive-inductive-capacitivesensors 402 and a consistent force activation threshold for eachresistive-inductive-capacitive sensor 402.

Although the foregoing contemplates compensator 552 integral toprocessing IC 512 as measuring phase information, calculatingcompensation factors, and applying such compensation factors, in someembodiments, all or part of compensator 552 may be implemented within acontroller (e.g., controller 103) external to processing IC 512.

Although the foregoing contemplates use of closed-loop feedback forsensing of displacement, the various embodiments represented by FIGS.5A-5C may be modified to implement an open-loop system for sensing ofdisplacement. In such an open-loop system, a processing IC 512 mayinclude no feedback path from amplitude and phase calculation block 531to oscillator 516 or variable phase shifter 519 and thus may also lack afeedback low-pass filter 534. Thus, a phase measurement may still bemade by comparing a change in phase to a reference phase value, but theoscillation frequency driven by oscillator 516 may not be modified orthe phase shifted by variable phase shifter 519 may not be shifted.

Although the foregoing contemplates use of a coherentincident/quadrature detector as a phase detector for determining phaseinformation associated with resistive-inductive-capacitive sensor 402, aresonant phase sensing system 112 may perform phase detection and/orotherwise determine phase information associated withresistive-inductive-capacitive sensor 402 in any suitable manner,including, without limitation, using only one of the incident path orquadrature path to determine phase information.

In some embodiments, an incident/quadrature detector as disclosed hereinmay include one or more frequency translation stages that translate thesensor signal into direct-current signal directly or into anintermediate frequency signal and then into a direct-current signal. Anyof such frequency translation stages may be implemented either digitallyafter an analog-to-digital converter stage or in analog before ananalog-to-digital converter stage.

In addition, although the foregoing contemplates measuring changes inresistance and inductance in resistive-inductive-capacitive sensor 402caused by displacement of mechanical member 105, other embodiments mayoperate based on a principle that any change in impedance based ondisplacement of mechanical member 105 may be used to sense displacement.For example, in some embodiments, displacement of mechanical member 105may cause a change in a capacitance of resistive-inductive-capacitivesensor 402, such as if mechanical member 105 included a metal plateimplementing one of the capacitive plates of capacitor 406.

Although DSP 532 may be capable of processing phase information to makea binary determination of whether physical interaction associated with ahuman-machine interface associated with mechanical member 105 hasoccurred and/or ceased to occur, in some embodiments, DSP 532 mayquantify a duration of a displacement of mechanical member 105 to morethan one detection threshold, for example to detect different types ofphysical interactions (e.g., a short press of a virtual button versus along press of the virtual button). In these and other embodiments, DSP532 may quantify a magnitude of the displacement to more than onedetection threshold, for example to detect different types of physicalinteractions (e.g., a light press of a virtual button versus a quick andhard press of the virtual button).

As used herein, when two or more elements are referred to as “coupled”to one another, such term indicates that such two or more elements arein electronic communication or mechanical communication, as applicable,whether connected indirectly or directly, with or without interveningelements.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Similarly,where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to the exampleembodiments herein that a person having ordinary skill in the art wouldcomprehend. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, or component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative. Accordingly, modifications, additions, oromissions may be made to the systems, apparatuses, and methods describedherein without departing from the scope of the disclosure. For example,the components of the systems and apparatuses may be integrated orseparated. Moreover, the operations of the systems and apparatusesdisclosed herein may be performed by more, fewer, or other componentsand the methods described may include more, fewer, or other steps.Additionally, steps may be performed in any suitable order. As used inthis document, “each” refers to each member of a set or each member of asubset of a set.

Although exemplary embodiments are illustrated in the figures anddescribed below, the principles of the present disclosure may beimplemented using any number of techniques, whether currently known ornot. The present disclosure should in no way be limited to the exemplaryimplementations and techniques illustrated in the drawings and describedabove.

Unless otherwise specifically noted, articles depicted in the drawingsare not necessarily drawn to scale.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the disclosureand the concepts contributed by the inventor to furthering the art, andare construed as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present disclosurehave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the disclosure.

Although specific advantages have been enumerated above, variousembodiments may include some, none, or all of the enumerated advantages.Additionally, other technical advantages may become readily apparent toone of ordinary skill in the art after review of the foregoing figuresand description.

To aid the Patent Office and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims or claimelements to invoke 35 U.S.C. § 112(f) unless the words “means for” or“step for” are explicitly used in the particular claim.

What is claimed is:
 1. A system comprising: a sensor configured tooutput a sensor signal indicative of a distance between the sensor and amechanical member associated with the sensor; a measurement circuitcommunicatively coupled to the sensor and configured to determine aphysical force interaction with the mechanical member based on thesensor signal; and a compensator configured to monitor the sensor signaland to apply a compensation factor to the sensor signal to compensatefor changes to properties of the sensor based on at least one of:changes in a distance between the sensor and the mechanical member; andchanges in a temperature associated with the sensor.
 2. The system ofclaim 1, wherein the sensor is a resistive-inductive-capacitive sensor.3. The system of claim 2, wherein: the system further comprises a driverconfigured to drive the sensor at a driving frequency; and themeasurement circuit is configured to: measure phase informationassociated with the sensor; and based on the phase information,determine a displacement of a mechanical member relative to theresistive-inductive-capacitive sensor, wherein the displacement of themechanical member causes a change in an impedance of theresistive-inductive-capacitive sensor.
 4. The system of claim 3, whereinthe displacement is indicative of an interaction with a virtual buttoncomprising the mechanical member.
 5. The system of claim 4, wherein thecompensator is further configured to apply the compensation factor toconsistently determine interaction with the virtual button despitechanges in properties of the sensor.
 6. The system of claim 1, whereinthe compensator is further configured to: determine a resonant frequencyof the sensor; and determine a change in one or more of the distancebetween the sensor and the mechanical member and the temperature basedon the resonant frequency.
 7. The system of claim 1, wherein thecompensator is further configured to: determine a resonant frequency ofthe sensor; and determine a change in an impedance of the sensor basedon the frequency.
 8. The system of claim 1, wherein the compensator isfurther configured to: determine a resonant frequency of the sensor; anddetermine a change in an inductance of the sensor based on thefrequency.
 9. The system of claim 1, wherein the compensator is furtherconfigured to determine a change in the distance between the sensor andthe mechanical member based on the change in inductance.
 10. The systemof claim 1, wherein the compensator applies the compensation factor inresponse to one or more of: a change in resonant frequency of the sensorby more than a threshold frequency change; a change in resonantfrequency of the sensor at a rate outside of a predetermined frequencyrate change range; a change in a quality factor of the sensor by morethan a threshold quality factor change; and a change in the qualityfactor of the sensor at a rate outside of a predetermined quality factorrate change range.
 11. The system of claim 1, wherein the compensatorcomprises a quality factor detector configured to monitor a qualityfactor of the sensor and the compensator is configured to apply thecompensation factor based on the quality factor.
 12. The system of claim11, wherein the compensator is configured to determine a temperatureassociated with the sensor based on the quality factor.
 13. The systemof claim 1, wherein the compensation factor comprises one or more of:scaling of measured phase information associated with the sensor;scaling of measured amplitude information associated with the sensor;modification of a detection threshold for indicating physical forceinteraction with the mechanical member; application of an offset to thesensor signal; application of a filter to the sensor signal; applicationof a compensation value from a lookup table; and modification of aresonant frequency of the sensor.
 14. The system of claim 1, wherein thecompensator is further configured to: determine impedance of the sensoras a function of frequency; determine a calculated inductance of thesensor based on the impedance of the sensor as a function of frequency;compare the calculated inductance against a predetermined inductanceversus distance relationship of the sensor to determine the distancebetween the mechanical member and the sensor; and apply the compensationas a gain correction to compensate for changes in the distance.
 15. Thesystem of claim 1, wherein the compensator is further configured to:over a duration, linearly increase a current driven to the sensor from aminimum current to a maximum current; measure a voltage associated withthe sensor during the duration; determine a calculated inductance of thesensor based on the voltage, the maximum current and the minimumcurrent; compare the calculated inductance against a predeterminedinductance versus distance relationship of the sensor to determine thedistance between the mechanical member and the sensor; and apply thecompensation as a gain correction to compensate for changes in thedistance.
 16. The system of claim 1, wherein the compensator is furtherconfigured to: during an initial calibration, determine a phase responseof the sensor as a function of force applied to the mechanical member;and based on the phase response, determine the compensation to beapplied to the sensor signal to achieve a desired phase response for thesensor.
 17. The system of claim 1, wherein: the system comprises aplurality of sensors including the sensor; and the compensator isfurther configured to: during an initial calibration: determine a phaseresponse of each sensor as a function of force applied to the mechanicalmember; and calculate a plurality of calibrated ratios of the phaseresponses between adjacent sensors of the plurality of sensors duringthe initial calibration; and during an operation: determine the phaseresponse of each sensor as a function of force applied to the mechanicalmember; calculate a plurality of monitored ratios of the phase responsesbetween adjacent sensors of the plurality of sensors during operation;and apply the compensation to one or more of the plurality of sensorsbased on differences between the monitored ratios and the calibratedratios.
 18. A method comprising, in a system comprising a sensorconfigured to output a sensor signal indicative of a distance betweenthe sensor and a mechanical member associated with the sensor and ameasurement circuit communicatively coupled to the sensor and configuredto determine a physical force interaction with the mechanical memberbased on the sensor signal: monitoring the sensor signal; and applying acompensation factor to the sensor signal to compensate for changes toproperties of the sensor based on at least one of: changes in a distancebetween the sensor and the mechanical member; and changes in atemperature associated with the sensor.
 19. The method of claim 18,wherein the sensor is a resistive-inductive-capacitive sensor.
 20. Themethod of claim 19, wherein: the system further comprises a driverconfigured to drive the sensor at a driving frequency; and themeasurement circuit is configured to: measure phase informationassociated with the sensor; and based on the phase information,determine a displacement of a mechanical member relative to theresistive-inductive-capacitive sensor, wherein the displacement of themechanical member causes a change in an impedance of theresistive-inductive-capacitive sensor.
 21. The method of claim 20,wherein the displacement is indicative of an interaction with a virtualbutton comprising the mechanical member.
 22. The method of claim 21,further comprising applying the compensation factor to consistentlydetermine interaction with the virtual button despite changes inproperties of the sensor.
 23. The method of claim 18, furthercomprising: determining a resonant frequency of the sensor; anddetermining a change in one or more of the distance between the sensorand the mechanical member and the temperature based on the resonantfrequency.
 24. The method of claim 18, further comprising: determining aresonant frequency of the sensor; and determining a change in animpedance of the sensor based on the frequency.
 25. The method of claim18, further comprising: determining a resonant frequency of the sensor;and determining a change in an inductance of the sensor based on thefrequency.
 26. The method of claim 18, further comprising determining achange in the distance between the sensor and the mechanical memberbased on the change in inductance.
 27. The method of claim 18, furthercomprising applying the compensation factor in response to one or moreof: a change in resonant frequency of the sensor by more than athreshold frequency change; a change in resonant frequency of the sensorat a rate outside of a predetermined frequency rate change range; achange in a quality factor of the sensor by more than a thresholdquality factor change; and a change in the quality factor of the sensorat a rate outside of a predetermined quality factor rate change range.28. The method of claim 18, further comprising monitoring a qualityfactor of the sensor and the compensator is configured to apply thecompensation factor based on the quality factor.
 29. The method of claim28, further comprising determining a temperature associated with thesensor based on the quality factor.
 30. The method of claim 18, whereinthe compensation factor comprises one or more of: scaling of measuredphase information associated with the sensor; scaling of measuredamplitude information associated with the sensor; modification of adetection threshold for indicating physical force interaction with themechanical member; application of an offset to the sensor signal;application of a filter to the sensor signal; application of acompensation value from a lookup table; and modification of a resonantfrequency of the sensor.
 31. The method of claim 18, further comprising:determining impedance of the sensor as a function of frequency;determining a calculated inductance of the sensor based on the impedanceof the sensor as a function of frequency; comparing the calculatedinductance against a predetermined inductance versus distancerelationship of the sensor to determine the distance between themechanical member and the sensor; and applying the compensation as again correction to compensate for changes in the distance.
 32. Themethod of claim 18, further comprising: over a duration, linearlyincreasing a current driven to the sensor from a minimum current to amaximum current; measuring a voltage associated with the sensor duringthe duration; determining a calculated inductance of the sensor based onthe voltage, the maximum current and the minimum current; comparing thecalculated inductance against a predetermined inductance versus distancerelationship of the sensor to determine the distance between themechanical member and the sensor; and applying the compensation as again correction to compensate for changes in the distance.
 33. Themethod of claim 18, further comprising: during an initial calibration,determining a phase response of the sensor as a function of forceapplied to the mechanical member; and based on the phase response,determining the compensation to be applied to the sensor signal toachieve a desired phase response for the sensor.
 34. The method of claim18, wherein the system comprises a plurality of sensors including thesensor, and the method further comprises, during an initial calibration:determining a phase response of each sensor as a function of forceapplied to the mechanical member; and calculating a plurality ofcalibrated ratios of the phase responses between adjacent sensors of theplurality of sensors during the initial calibration; and during anoperation: determining the phase response of each sensor as a functionof force applied to the mechanical member; calculating a plurality ofmonitored ratios of the phase responses between adjacent sensors of theplurality of sensors during operation; and applying the compensation toone or more of the plurality of sensors based on differences between themonitored ratios and the calibrated ratios.